An Investigation into, and Improvement of, the Non-uniformity of the Flow Field caused by the Pumping Effect in a Stagnation Flow CVD Reactor

To deposit a film with uniform thickness, flow rectifiers are often used in a CVD reactor. Despite the effectiveness of these rectifiers, some degree of flow non-uniformity persists within the reaction chamber, due to variations in the flow and buoyancy effects. Here, the non-uniformity caused by the non-axisymmetric pumping system, specifically a single and non-annular pumping outlet, is investigated. A pumping liner, which directs the fluid mixture through embedded channels into a ring chamber connected to the pumping outlet, is used to improve flow uniformity. The flow resistance associated with each component in the pumping system is analyzed, then two carefully designed pumping liners, the channels of which either have non-uniform radii or are unevenly spaced, are proposed. The pumping effect is balanced through the non-uniform channel flow resistances, giving an axisymmetric flow field in the reaction chamber. This balance is confirmed in simulations.